Device for rapid exchange of ion sources and ion transmission devices

ABSTRACT

A mass spectrometer is disclosed comprising a rotatable isolation valve 1 having a curved, spherical, cylindrical or concave portion. At least a portion of an ion guide 2 is positioned so as to extend within a swept volume of the isolation valve 1 enabling the ion guide 2 to be positioned close to a second downstream ion guide 3 and for ions to be transmitted from the first 2 ion guide to the second ion guide 3 with high ion transmission efficiency.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/956,922, filed on Jun. 22, 2020, which is a national phase filingclaiming the benefit of and priority to International Patent ApplicationNo. PCT/GB2018/053747, filed on Dec. 21, 2018, which claims priorityfrom and the benefit of United Kingdom patent application No. 1721834.8,filed on Dec. 22, 2017 and United Kingdom patent application No.1721836.3, filed on Dec. 22, 2017. The entire contents of theseapplications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to the field of massspectrometry.

BACKGROUND

Mass spectrometers comprising a Matrix Assisted Laser DesorptionIonisation (“MALDI”) ion source are known. Matrix Assisted LaserDesorption Ionisation (“MALDI”) mass spectrometry is a known processwhich is particularly suited for the analysis of non-volatilebiomolecules. A suitable matrix material (e.g. an organic solvent) isadded to a sample so that the sample becomes embedded in the matrixmaterial. The embedded sample is then positioned on a metal plate and alaser pulse is directed on to the target sample. The laser pulseimpinging upon the target sample causes analyte material to be ablatedand desorbed from the target sample. Analyte ions are generated byanalyte material being protonated or deprotonated in a hot plume ofgaseous molecules which is released from the target. The matrix has astrong absorption at the wavelength of the laser pulse and acts as aproton source to encourage ionisation of the analyte. The gaseous plumewhich is released from the target comprises a mixture of analyte ionstogether with neutral particles. The mixture of analyte ions and neutralparticles is then directed towards the inlet of a mass spectrometer. Theanalyte ions are separated from the neutral particles with the analyteions being onwardly transmitted to a mass analyser of the massspectrometer in order to be mass analysed.

Matrix Assisted Laser Desorption Ionisation mass spectrometry imaging(“MALDI-MSI”) involves analysing the distribution of biomolecules acrossthe surface of a target (e.g. a tissue embedded in a matrix) by scanningthe target with a focused laser beam and recording the ion profile ateach irradiated pixel. An image of the mass spectral properties of thetarget across the surface of the target can then be constructed.

According to a known mass spectrometer comprising a Matrix AssistedLaser Desorption Ionisation (“MALDI”) ion source analyte ions generatedby the ion source are onwardly transmitted to further stages of the massspectrometer via a first rod set ion guide which is provided in a firstor initial vacuum chamber of the mass spectrometer.

One problem with the known arrangement is that the first rod set ionguide can become contaminated or the rod electrodes comprising the firstrod set ion guide may otherwise become dirty or coated with analyte andbackground material. In particular, ions and neutral particles mayimpact the outer surface of the electrodes forming the first rod set ionguide over a period of time so that the electrodes forming the first rodset ion guide become coated with insulating material which degrades theperformance of the first rod set ion guide and hence negatively impactsthe overall performance of the mass spectrometer.

In order to maintain performance of the first rod set ion guide and theoverall mass spectrometer it is necessary periodically to remove thefirst rod set ion guide from the first or initial vacuum chamber of themass spectrometer in order to clean the first rod set ion guide byremoving any surface build up of contaminants on the surface of theelectrodes of the first rod set ion guide.

However, the process of removing the first rod set ion guide from thefirst vacuum chamber of the known mass spectrometer is relativelycomplex and time consuming. The first rod set ion guide of the knownarrangement is not readily removeable from the vacuum chamber of themass spectrometer in which it is housed. As will be understood by thoseskilled in the art, the first rod set ion guide and the geometry of thevacuum chamber is such that the first rod set ion guide can not beserviced by non-skilled users. In particular, it requires the servicesof a skilled service engineer in order to remove the first rod set ionguide from the first vacuum chamber of the mass spectrometer.

Furthermore, the process of removing the first rod set ion guide fromthe first vacuum chamber of the mass spectrometer for cleaning purposesinvolves fully venting the mass spectrometer prior to removal of thefirst rod set ion guide from the first vacuum chamber.

It will be understood by those skilled in the art that the process ofestablishing a high vacuum (low pressure) in a downstream analyser stageof a mass spectrometer is a time consuming process. Accordingly, theconventional approach to cleaning the first rod set ion guide of a massspectrometer is both relatively complex in that it requires the servicesof a skilled engineer as well as being relatively time consuming in thatthe mass spectrometer will be offline for a period of time whilst themass spectrometer is initially fully vented. Furthermore, once the firstrod set ion guide has been removed, cleaned and reinstalled in the firstvacuum chamber of the mass spectrometer it then takes a considerableperiod of time in order to reestablish a high vacuum (low pressure) inthe downstream analyser stage of the mass spectrometer.

In an analagous manner, conventionally if it is desired to remove asub-atmospheric pressure ion source housed in a vacuum chamber of themass spectrometer in order to operate a different type of ion sourcethen this similarly involves the complete venting of the instrument.Accordingly, conventionally seeking to change a sub-atmospheric pressureion source for an atmospheric pressure ion source can be a relativelycomplex and time consuming process requiring the services of a skilledengineer.

It is desired to provide an improved mass spectrometer.

SUMMARY OF THE INVENTION

According to an aspect there is provided apparatus comprising:

-   -   a vacuum chamber;    -   an isolation valve having a curved, spherical, cylindrical or        concave portion; and    -   a first ion guide, wherein at least a portion of the first ion        guide extends, in use, within a swept volume of the isolation        valve or within the curved, spherical, cylindrical or concave        portion of the isolation valve.

The apparatus may, for example, comprise an analytical device, a massspectrometer or an ion mobility spectrometer.

The curved shape or profile of the isolation valve allows the first ionguide to cooperate with the isolation valve so that an end of the firstion guide sits within a swept volume of the isolation valve. Accordingto various embodiments the isolation valve is rotatable and as theisolation valve is rotated the profile of the isolation valve sweeps outa volume which may be referred to as a “swept volume” as will beunderstood by those skilled in the art. The positioning of at least aportion of the first ion guide within a swept volume of the isolationvalve (or within a curved, spherical, cylindrical or concave portion ofthe isolation valve) and the curved, spherical, cylindrical or concavenature of the isolation valve enables a compact design to be providedand enables a downstream end of the first ion guide to be located closeto the entrance of a downstream second ion guide thereby ensuring highion transmission efficiency between the two ion guides.

The contours of the isolation valve and the arrangement of electrodesforming the first ion guide (which may be arranged upstream of theisolation valve) and/or the arrangement of electrodes forming a secondion guide (which may be arranged downstream of the isolation valve) maybe designed to accommodate the isolation valve in an optimum manner. Inparticular, the electrodes of the first upstream ion guide may bearranged so that the electrodes of the first ion guide extend within andinto the swept volume of the isolation valve so as to minimise thedistance between the exit or a downstream end of the first ion guide andthe entrance or an upstream end of a second downstream ion guide locateddownstream of the first ion guide and the isolation valve. Inparticular, when the isolation valve is positioned in an open positionin normal operation then the downstream end of the first ion guide maybe arranged so as to abut relatively closely to the entrance of thesecond downstream ion guide so as to provide high ion transmissionefficiency between the two ion guides whilst also allowing the isolationvalve to be closed in a mode of operation so as to isolate thedownstream second ion guide from the upstream first ion guide.

The curved shape or profile of the isolation valve allows the isolationvalve to be positioned in close proximity to a second ion guide whichmay be arranged downstream of the first ion guide. As a result, thefirst and second ion guides can be located close to each other or inclose proximity to each other. The distance between the exit of thefirst rod set ion guide and the entrance to the second downstream ionguide can therefore be reduced or minimised enabling ions to betransferred efficiently from the first ion guide to the second ion guidewithout ion loss.

The isolation valve may be operable to enable a first ion optic assemblyto be removed from and/or inserted within a first upstream section of avacuum chamber at the same time as a second downstream section of thevacuum chamber is maintained at a lower pressure than the first upstreamsection of the vacuum chamber. The first ion optic assembly may compriseone or more first ion guides. For example, the one or more first ionguides may comprise a multipole rod set arrangement comprising aplurality of rod electrodes or a ring set arrangement of electrodes. Thefirst ion optic assembly may comprise a plurality of electrodes, whereinone or more of the electrodes extend within a swept volume of theisolation valve. The isolation valve may have or present a substantiallyconcave profile relative to the first ion optic assembly. The apparatusmay further comprise a second ion optic assembly arranged downstream ofthe isolation valve. The isolation valve may have or present asubstantially convex profile relative to the second ion optic assembly.The isolation valve may be rotatable or actuable between an openposition and a closed position. When the isolation valve is in an openposition the first upstream section of a vacuum chamber including thefirst ion optic assembly may be in fluid communication with the seconddownstream section of the vacuum chamber. When the isolation valve is ina closed position the first upstream section of the vacuum chamberincluding the first ion optic assembly is not in fluid communicationwith the second downstream section of the vacuum chamber therebyenabling the pressure within the first upstream section to be raised toatmospheric or ambient pressure whilst the second downstream section maybe maintained at a substantially lower pressure.

According to various embodiments a spherical or curved valve orisolation valve is provided which is capable of isolating a smallchamber containing a first ion guide from further stages of a massspectrometer. The provision of the isolation valve allows the instrumentvacuum to be maintained whilst venting the source. The isolation valvemay be provided in conjunction with an ion guide assembly having one ormore guide rails and the ion guide assembly may be retained in positionby one or more latching clip releases.

The overall arrangement enables a non-skilled user to perform variousfunctions such as closing the isolation valve in order to maintain thelow pressure (high vacuum) in downstream vacuum chambers of theinstrument and then remove and optionally clean and/or replace the firstion guide. It will be understood that conventionally such functions arereserved for skilled engineers. An analytical instrument, massspectrometer or ion mobility spectrometer according to variousembodiments therefore has an improved serviceability compared withconventional arrangements and in particular an analytical instrument,mass spectrometer or ion mobility spectrometer according to variousembodiments may be serviced by non-skilled users.

The isolation valve enables a source or ion source to be vented withoutthe requirement of venting an analyser which may be provided in adownstream analyser vacuum chamber.

According to various embodiments an isolation valve is provided whichallows a vacuum chamber containing or housing a first ion guide assemblyto be vented and opened without an analyser needing to be vented orfully vented.

Maintaining the vacuum in the analyser enables the voltages applied tothe electrodes inside the analyser to be maintained during cleaning andmaintenance of the first ion guide or first ion guide assembly with theresult that it is not necessary to re-calibrate the instrument uponreturn to operation.

The first ion guide may comprise a plurality of rod electrodes.

The first ion guide may comprise a multipole rod set. For example,according to various embodiments the first ion guide may comprise aquadrupole rod set ion guide, a hexapole rod set ion guide or anoctopole rod set ion guide. The first ion guide may comprise more thaneight rod electrodes.

One or more RF or AC voltages may be applied to the rod electrodes inorder to generate a pseudo-potential ion confinement region within avolume defined by the inscribed radius of the rod set electrodes.

The rod electrodes once removed from the vacuum chamber may be easilycleaned and reinserted into the instrument by a non-skilled user.

At least some of the rod electrodes may have a bevelled, curved ornon-planar portion or end which is located, in use, adjacent theisolation valve.

The curved shape or profile of the isolation valve and the bevelled,curved or non-planar portion or end of the first rod set ion guideenables the first ion guide to be positioned in close proximity to theisolation valve and in particular in close proximity with a curved,spherical, cylindrical or concave portion of the isolation valve.

The first ion guide may comprise a plurality of electrodes having anupstream end and a downstream end, wherein a portion or a downstream endof at least some or all of the electrodes is bevelled, curved ornon-planar.

The bevelled, curved or non-planar portion or end(s) of the first ionguide enables the ion guide to cooperate with the isolation valve sothat the end of the first ion guide sits within a swept volume of theisolation valve. As a result, a compact design is provided which enablesthe first ion guide to be located close to the entrance of a downstreamsecond ion guide thereby ensuring a high ion transmission efficiencybetween the two ion guides.

The first ion guide may comprise a ring set ion guide or a plurality ofelectrodes having apertures through which ions are transmitted in use.The electrodes forming the first ion guide may have an external diameteror profile and the external diameter or profile of one or moreelectrodes forming the first ion guide may reduce or taper towards adownstream section of the first ion guide.

The ring electrodes may have an internal diameter or first profile andan external diameter or second profile. The external diameter or secondprofile of one or more electrodes forming the first ion guide may reduceor taper towards a downstream section of the first ion guide so that thefirst ion guide extends, in use, within a swept volume or a curved,spherical, cylindrical or concave portion of the isolation valve. As aresult, the first ion guide can be located close to the entrance of adownstream second ion guide thereby ensuring a high ion transmissionefficiency between the two ion guides.

A downstream end of the first ion guide may be located, in use, 10 mmfrom the isolation valve.

According to various embodiments the first ion guide may be locatedparticularly close to the isolation valve or a curved, spherical,cylindrical or concave portion of the isolation valve in order toimprove ion transmission efficiency. For example, according to variousembodiments a downstream end of the first ion guide may be located ≤9mm, ≤8 mm, ≤7 mm, ≤6 mm, ≤5 mm, ≤4 mm, ≤3 mm, ≤2 mm or ≤1 mm from theisolation valve or a portion of the isolation valve.

The apparatus may further comprise a second ion guide, wherein in a modeof operation at least a portion of the isolation valve extends within aportion of the second ion guide.

The second ion guide may be located downstream of the isolation valveand/or downstream of the first ion guide. According to variousembodiments ions may be efficiently transmitted from the first ion guideto the second ion guide with essentially negligible loss of ions due tothe close packed arrangement between the first ion guide, the isolationvalve and the second ion guide.

The second ion guide may comprise a ring set ion guide or a plurality ofelectrodes having apertures through which ions are transmitted in use.

The second ion guide may comprise a plurality of ring electrodes whereinone or more RF or AC voltages may be applied to the ring electrodes inorder to generate a pseudo-potential ion confinement region within thering set or within the apertures of the electrodes.

According to various embodiments the second ion guide may comprise aStepWave® ion guide arrangement comprising a stacked ring ion guidewhich is arranged to maximise ion transmission from a source to a massanalyser. The device also allows for the active removal of neutralcontaminants, providing an enhancement to overall signal to noise. Thesecond ion guide may facilitate the efficient capture of a relativelydiffuse ion cloud entering the first stage, which is then focused intoan upper ion guide for transfer to the mass analyser.

The first ion guide may be located, in use, in the vacuum chamber andthe isolation valve may be operable to isolate a region downstream ofthe first ion guide.

For example, the isolation valve may be operable to isolate a portion ofa vacuum chamber or a vacuum chamber housing the first rod set ion guidefrom a second downstream ion guide. The second downstream ion guide maybe provided in the same vacuum chamber as the first ion guide oralternatively the second downstream ion guide may be provided in asecond or different vacuum chamber.

The isolation valve can be operated by a non-skilled user and enablese.g. a mass analyser to be maintained at a low pressure whilst the firstion guide is removed for servicing.

The apparatus may further comprise an analytical device, a mass analyseror an ion mobility spectrometer arranged downstream of the isolationvalve, wherein the isolation valve may be operated so as to maintain theanalytical device, mass analyser or ion mobility spectrometer at asub-atmospheric pressure whilst the first ion guide is removed.

The analytical device, mass analyser or ion mobility spectrometer may beprovided in a vacuum chamber which may be maintained, in use, at arelatively low pressure. For example, according to various embodimentsthe vacuum chamber housing the analytical device or mass analyser may bemaintained at a pressure ≤10⁻³ mbar whilst the first rod set ion guideis removed. According to other embodiments the vacuum chamber housingthe analytical device or mass analyser may be maintained at a pressure≤10⁻⁴ mbar, ≤10⁻⁵ mbar, ≤10⁻⁶ mbar, ≤10⁻⁷ mbar or ≤10⁻⁸ mbar whilst thefirst rod set ion guide is removed. It will be understood thatmaintaining the analytical device or mass analyser at sub-atmosphericpressure whilst the first rod set ion guide is removed (at atmosphericor ambient pressure) and serviced reduces the downtime of the instrumentand removes any need to recalibrate the instrument.

The isolation valve may be rotatable between an open position and aclosed position.

The curved shape or profile of the isolation valve enables the isolationvalve to be rotated from an open position to a closed position in acompact manner enabling close positioning of the first and second ionguides.

According to an aspect there is provided a method comprising:

guiding ions through a first ion guide, wherein at least a portion ofthe first ion guide extends, in use, within a swept volume of anisolation valve or within a curved, spherical, cylindrical or concaveportion of an isolation valve.

The method may further comprise operating the isolation valve so as tomaintain an analytical device, a mass analyser or an ion mobilityspectrometer at a sub-atmospheric pressure whilst the first ion guide isremoved.

The method may further comprise rotating the isolation valve between anopen position and a closed position.

According to another aspect there is provided apparatus comprising:

a vacuum chamber;

a housing located within the vacuum chamber and having a guidemechanism; and

a first ion optic assembly which is slidable or translatable incooperation with the guide mechanism thereby enabling the first ionoptic assembly to be inserted and aligned within the vacuum chamber.

A MALDI mass spectrometer is known having an ion guide assembly locatedwithin a vacuum chamber. However, the ion guide assembly of the knownarrangement is not readily removeable and requires tools in order tounfasten and remove the ion guide assembly from the vacuum chamber. Aswill be understood by those skilled in the art, removing the ion guideassembly of the known mass spectrometer requires the services of askilled engineer. Removing an ion guide assembly from the vacuum chamberof a conventional mass spectrometer also requires that the MALDI ionsource is retracted from the vacuum chamber so that the ion guideassembly can then be manipulated out through a lid in the housing of thevacuum chamber. This is problematic for a number of reasons.

Firstly, during its manipulation, extraction and replacement, a mirrorinside the vacuum chamber which provides a viewing window for a MALDIcamera can be caught and displaced from its critical alignment.

Secondly, the voltages that are provided to the electrodes that comprisethe known ion guide assembly are delivered using wires and connectorsthat are part of the ion guide assembly. During its manipulation, thewires can become caught or dislodged resulting in a risk of closeproximity or contact with other electrodes or components consequentlycausing an increased risk of electrical breakdown once returned to anoperational state.

In contrast to the known arrangement, according to various embodiments ahousing is provided within a vacuum chamber and the housing may includeguided bearings which ensure that a first ion optic assembly, ion guideor ion transmission device can be removed and/or (re-)inserted withoutthe risk of moving or damaging any of the parts inside the chamber orvacuum chamber.

According to various embodiments a guide rail and associated guidebearings may be provided which allow one or more laser mirrors to bepositioned close to the ion optic axis of the ion guide thereby enablinga laser beam to be delivered to a sample at an angle close to normalincidence whilst also reducing the overall working distance between thefocusing lens and the sample plate. This has a number of benefits.

Firstly, the reduced angle of incidence reduces the degree of distortionof the incident beam resulting in a more circular illumination of thesample.

Secondly, the ability to include a shorter focal length lens means thatthe incident laser beam can be more tightly focused on to the sampleplate, enabling increased spatial resolution of the locality of thedetected ions.

When loading or unloading a sample on a conventional MALDI ion source, asample plate carrier must travel to a load lock location before sealingagainst a door. The load lock chamber is then vented. By isolating theanalyser vacuum using an isolation valve according to variousembodiments and venting the entire chamber there is no requirement forthe sample plate carrier to be moved. This reduces the time it takes tounload a sample.

Another problem with the conventional load lock system is the risk that,during loading, a difference between the pressure that is achieved inthe load lock chamber and the sample chamber can result in sudden gasflow from the load lock into the sample chamber as the sample carrierretracts from the load lock seal. On occasions, this can result insample plates falling from the carrier into the main sample vacuumchamber during this transition, resulting in a need to dismantle thewhole of the sample chamber in order to retrieve the sample.

In contrast to the known arrangement, the sample chamber according tovarious embodiments may be fully opened allowing any sample that fallsoff the carrier to be retrieved easily.

Another benefit of the removal of a load lock is that larger sampleplates can be used whilst maintaining a similar length of leadscrew.

Conventionally, changeover from one ion source to another currentlyrequires the complete venting of the instrument. The combination of theisolation valve and the guide bearings and/or a rail configurationaccording to various embodiments allows the first ion guide assembly tobe removed and replaced with an assembly suitable for alternative ionsources without the need to vent the entire instrument.

According to various embodiments an ion guide may be mounted to anassembly which may comprise a guided mounting mechanism. The combinationof a vacuum isolation valve and a guided mounting mechanism for an ionguide (which may also have an integrated latch and seal mechanism)enables rapid exchange of an initial or first ion guide and reduces thedowntime of a mass spectrometer or other analytical instrument beingtaken offline for servicing.

The cooperation between the first ion optic assembly and the guidemechanism allows the first ion optic assembly to be removed from thevacuum chamber without becoming tangled or caught with wires orelectrical cables. Furthermore, the first ion optic assembly can beinserted and/or removed from the vacuum chamber without any risk ofdamaging other components including sensitive ion optical components,laser mirrors and the like.

The apparatus according to various embodiments enables the first ionguide of an analytical instrument, mass spectrometer or ion mobilityspectrometer to be removed easily for cleaning. After cleaning, the ionguide can be replaced easily by a non-skilled user i.e. a specialistservice engineer is not required. In particular, mounting the first ionguide as part of an ion optic assembly and being able to axially slideor translate the first ion guide and associated ion optic assembly intoand out of a first (or subsequent) vacuum chamber optionally in thedirection of the ion optic axis (i.e. axially) enables a non-skilleduser to insert and/or remove a first ion guide without specialist skill.The first ion optic assembly may be provided with a guide mechanism suchas one or more guide rails. The guide rails may slide into or engagewith one or more guide bearings optionally mounted on a second assemblyor a housing which may be arranged to connect with or interlock with thefirst assembly which may house or include the first ion guide.

The guide rail mechanism according to various embodiments isparticularly effective at ensuring and facilitating easy alignment ofthe first ion guide with the rest of the housing of the analyticalinstrument, mass spectrometer or ion mobility spectrometer and inensuring correct and precise positioning of the first ion guide withinthe first vacuum chamber of an analytical instrument such as a massspectrometer or ion mobility spectrometer.

Embodiments are contemplated wherein the guide mechanism may comprise adifferent form of sliding mechanism or wherein the tracks or guides mayhave different profiles at different axial positions.

Although various embodiments are disclosed wherein the assembly housingthe first ion guide comprises one, two or more than two guide railswhich slide within or engage with one, two or more than two guidebearings mounted to a second assembly or housing, other embodiments arecontemplated wherein the first ion guide assembly may comprise one, twoor more than two guide bearings and the second assembly or housing maycomprise one, two or more than two guide rails.

The guide mechanism may enable the first ion optic assembly to slide ortranslate in an axial direction thereby enabling the first ion opticassembly to be removed from and/or inserted within a chamber or vacuumchamber of an analytical instrument such as a mass spectrometer or ionmobility spectrometer.

The first ion optic assembly may further comprise a sealing memberhaving an ion inlet orifice therewithin, wherein the sealing member isarranged to seal against a front portion of the vacuum chamber.

The sealing member may form a vacuum tight seal with the front portionof the chamber or vacuum chamber with the exception of the ion inletorifice provided in the sealing member. Optionally, the sealing membermay include one or more O-ring seals for sealing against the frontportion of the vacuum chamber. However, the provision of one or moreO-rings is not essential. Accordingly, the sealing member of the firstion optic assembly may seal against the front portion of the chamber orvacuum chamber and pressure may effectively only be equalised via theion inlet orifice.

The apparatus may further comprise a releasable latch for securing thesealing member against the front portion of the vacuum chamber and/orfor securing the first ion optic assembly within the vacuum chamber.

The releasable latch enables the first ion optic assembly to be securedto a front face of a chamber or a vacuum chamber in a manner whichenables a non-skilled user to remove or withdraw the first ion opticassembly from the vacuum chamber without the use of tools.

The first ion optic assembly may further comprise a first electricalconnector and the housing may further comprise a second electricalconnector, wherein in use insertion of the first ion optic assembly intothe vacuum chamber causes the first electrical connector to connect withthe second electrical connector.

According to various embodiments contact pins and plates may be used toprovide electrical connections to the ion guide or first ion guide. Theuse of contact pins and plates according to various embodiments removesany risk of wires moving or becoming tangled. Furthermore, the guiderail mechanism prevents accidental clashes with any critically alignedcomponents inside the chamber or vacuum chamber such as laser mirrors.

One problem with the known MALDI mass spectrometer is thatconventionally the first ion guide located within a vacuum chamber has aseries of relatively complex electrical connections which need to bedisconnected and then reconnected before the first ion guide can beremoved and service. The disconnection and reconnection of theelectrical supplies to the first ion guide of the known MALDI massspectrometer requires the services of a skilled engineer.

However, in contrast to the known arrangement according to variousembodiments electrical connections to the ion guide or first ion guidemay be made via spring contacts inside the chamber or vacuum chamber.Accordingly, the ion guide or first ion guide can be disconnected and/orreconnected to an electrical supply in a simple manner which does notrequire the services of a skilled engineer.

A small roughing pump may be connected to a pumping port in the vacuumchamber enabling the pressure in the vacuum chamber to be reduced to alevel sufficient to open the isolation valve once the source or ionsource and the first ion guide are in position.

In contrast to the known arrangement, the electrical connections to thefirst ion guide may be disconnected from (and reconnected to) itselectrical power supply in a safe manner without requiring the servicesof a skilled engineer. Furthermore, the electrical connections are keptaway from an upstream end of the first ion guide thereby improving boththe safety and serviceability of the analytical instrument, massspectrometer or ion mobility spectrometer and improving the process ofremoving, cleaning and reinserting the first ion guide from and into thechamber or first vacuum chamber.

According to various embodiments contact pins and plates may be used toprovide electrical connections to the ion guide or first ion guide. Theuse of contact pins and plates according to various embodiments removesany risk of wires moving and enables a first ion guide to beelectrically connected and/or disconnected to an associated power supplywithout requiring a specialist service engineer. The connectors may bepositioned so as to connect with a rear (downstream) portion of thefirst ion guide thereby keeping the connection to an associated powersupply away from a user. Accordingly, the design enables electricalcontact to be made to and broken with the ion guide in a safe mannerwithout requiring specialist skill.

The first ion optic assembly may comprise one or more guide mechanisms,one or more guide rails or one or more guide bearings arranged toreceive one or more guide rails. The apparatus may further comprise asecond assembly which is arranged to connect with, secure to orinterlock with the first ion optic assembly. The second assembly may bearranged and adapted to facilitate alignment of the first ion opticassembly when the first ion optic assembly is inserted into the vacuumchamber. The second assembly may comprise one or more guide mechanisms,one or more guide rails or one or more guide bearings arranged toreceive one or more guide rails. The first ion optic assembly maycomprise one or more first electrical contacts which in use engage withone or more second electrical contacts provided on the second assembly.The one or more first electrical contacts may be retractable and/or theone or more second electrical contacts may be retractable. The guidemechanism may be arranged so as to enable the ion optic assembly toslide or translate in an axial direction which is substantially parallelto an ion optic axis.

The first ion optic assembly and/or a portion of the vacuum chamber maycomprise a spring release mechanism allowing the first ion opticassembly to be releasably secured to a portion of the vacuum chamber.The first ion optic assembly may further comprise one or more extractionelectrodes having one or more apertures through which ions aretransmitted in use. According to various embodiments either: (i) the oneor more apertures may be sized so as not to form a differential pumpingaperture; or (ii) the one or more apertures may be sized so as to form adifferential pumping aperture.

The first ion optic assembly may form a seal with a front face of thevacuum chamber or a front face of a mass spectrometer.

The first ion optic assembly may comprise a consumable component whichis replaced when contaminated.

According to another aspect there is provided a method comprising:

sliding or translating a first ion optic assembly in cooperation with aguide mechanism of a housing located within a vacuum chamber therebyenabling the first ion optic assembly to be inserted and aligned withinthe vacuum chamber.

According to an aspect there is provided apparatus comprising:

a vacuum chamber having an ion inlet orifice; and

an assembly housing a first sub-atmospheric pressure ion source, whereinin a first mode of operation the assembly may be secured to the vacuumchamber so as to align the first ion source with the ion inlet orificeand wherein in a second mode of operation the assembly may be detachedthereby enabling a second different ion source to be located adjacentthe ion inlet orifice.

Conventionally, changeover from one ion source to another may be arelatively a difficult process. According to various embodiments theapparatus comprises an assembly housing a first sub-atmospheric pressureion source. In a first mode of operation the assembly may be secured tothe vacuum chamber so as to align the first ion source with the ioninlet orifice and in a second mode of operation the assembly may bedetached thereby enabling a second different ion source to be locatedadjacent the ion inlet orifice. As a result, a non-skilled user mayoperate a sub-atmospheric pressure ion source located within a housingof an assembly and then simply detach the assembly in order to use adifferent ion source. For example, the second ion source may comprise anatmospheric pressure ion source.

According to various embodiments the assembly or door assembly which wasused in a first mode of operation may be re-used to provide a supportfor a second different ion source. However, whereas in the first mode ofoperation the assembly or door assembly may have made a vacuum tightseal against a front face of the vacuum chamber or a vacuum chamber, inthe second mode of operation the assembly or door assembly may be usedsimply as a support for the second ion source i.e. in the second mode ofoperation the assembly or door assembly may not make a tight sealagainst the front face of the vacuum chamber or a vacuum chamber.

Conventionally, changeover from one ion source to another requires thecomplete venting of the instrument. According to various embodiments thecombination of an isolation valve and guide bearings and/or a railconfiguration allows a first ion guide assembly to be removed andreplaced with an assembly suitable for alternative ion sources withoutthe need to vent the entire instrument.

The assembly may comprise a door assembly.

The apparatus may comprise an ion source housing which forms a seal withthe front face of a vacuum chamber or a front face of the massspectrometer.

The apparatus may further comprise a sub-atmospheric pressure ion sourceprovided or located within the ion source housing.

The ion source housing may comprise a removable door assembly.

The apparatus may further comprise an atmospheric pressure ion sourcewhich may be used in a second mode of operation.

According to various embodiments a sub-atmospheric pressure ion source,such as a Matrix Assisted Laser Desorption Ionisation (“MALDI”) ionsource, may be provided in the door assembly which may be secured to thevacuum chamber. The assembly or door assembly can be easily detachedfrom the vacuum chamber enabling a different type of ion source to beused.

The assembly may comprise a translation stage.

According to various embodiments the assembly may comprise an x-ytranslation stage for translating a sample plate such as a MALDI sampleplate in one or more orthogonal directions. In particular, a laser beammay be arranged to emerge from the apparatus via the ion inlet orifice.One or more sample regions to be ionised by the laser beam may betranslated into position using the translation stage.

In the first mode of operation the translation stage may be translatedin a first direction perpendicular to a direction of ion transmissionthrough the ion inlet orifice and/or in a second direction perpendicularto a direction of ion transmission through the ion inlet orifice,wherein the first direction is perpendicular to the second direction.

According to various embodiments the assembly and translation stage mayin the first mode of operation be arranged so as to translate e.g. asample plate in an x-direction and/or a y-direction wherein thex-direction and/or the y-direction are also orthogonal to an ion-opticalaxis or z-direction which may pass through the ion inlet orifice.

The first ion source may comprise a Matrix Assisted Laser DesorptionIonisation (“MALDI”) ion source.

The source or ion source may comprise a MALDI ion source although itshould be understood that the present invention is not limited to theuse of a MALDI ion source. If a MALDI ion source is provided then thesample chamber may be enclosed and operated under vacuum. According tovarious embodiments a MALDI ion source may be provided within anenclosure or housing which may form part of the assembly or doorassembly which may engage with or secure to the front end of the massspectrometer (or other analytical instrument) or the front end of avacuum chamber or the first vacuum chamber. A small pump may be includedto rough pump the sample chamber or housing prior to opening anisolation valve and exposing the source or ion source to the instrumentvacuum.

MALDI acquisitions generate a plume of material when a laser fires at atarget. Some of the plume of material is ionised and is onwardlytransmitted into the analyser whilst neutral species spread within thefirst vacuum chamber and are deposited on the localised surfaces. Overtime, and use, this deposit on the surface of the electrodes can affectthe electric fields generated by the electrodes and be detrimental tothe sensitivity of the instrument. As a result, the first ion guideassembly requires cleaning periodically.

Conventional MALDI ion sources coupled to a mass spectrometer requirethat the instrument is fully vented in order to remove a first ionguide. In contrast, an instrument according to various embodiments doesnot need to be fully vented prior to removing a first ion guide.

In the second mode of operation the assembly may be attached to thevacuum chamber or another part of the apparatus.

According to various embodiments the assembly or door assembly which wasused in a first mode of operation may be re-used to provide a supportfor a second different ion source. However, whereas in the first mode ofoperation the assembly or door assembly may have made a vacuum tightseal against a front face of the vacuum chamber or a vacuum chamber, inthe second mode of operation the assembly or door assembly may be usedsimply as a support for the second ion source i.e. in the second mode ofoperation the assembly or door assembly may not make a tight sealagainst the front face of the vacuum chamber or a vacuum chamber.

In the second mode of operation the assembly may include a translationstage, wherein the translation stage may be translated in a firstdirection parallel to a direction of ion transmission through the ioninlet orifice and/or in a second direction perpendicular to a directionof ion transmission through the ion inlet orifice.

According to various embodiments the assembly and translation stage mayin the second mode of operation be arranged so as to translate e.g. asample plate in an x-direction (or a y-direction) and/or in az-direction which may pass through the ion inlet orifice and which isparallel to an ion-optical axis.

The second ion source comprises at atmospheric pressure ion source.

For example, the second ion source may comprises a DesorptionElectrospray Ionisation (“DESI”) ion source, a Low Temperature Plasma(“LTP”) ion source, a Direct Analysis in Real Time (“DART”) ion sourceor an Inductively Coupled Plasma (“ICP”) ion source.

According to another aspect there is provided a method comprising:

securing an assembly housing a first sub-atmospheric pressure ion sourceto a vacuum chamber having an ion inlet orifice so as to align the firstion source with the ion inlet orifice; and then

detaching the assembly and locating a second different ion sourceadjacent the ion inlet orifice.

The assembly may comprise a translation stage and the method may furthercomprise translating the translation stage in a first directionperpendicular to a direction of ion transmission through the ion inletorifice and/or in a second direction perpendicular to a direction of iontransmission through the ion inlet orifice, wherein the first directionis perpendicular to the second direction.

The method may further comprise attaching the assembly to the vacuumchamber.

The assembly may include a translation stage and the method may furthercomprise translating the translation stage in a first direction parallelto a direction of ion transmission through the ion inlet orifice and/orin a second direction perpendicular to a direction of ion transmissionthrough the ion inlet orifice.

According to an aspect there is provided apparatus comprising:

a vacuum chamber having an ion inlet orifice; and

an assembly housing a first sub-atmospheric pressure ion source, whereinin a first mode of operation the assembly may be secured to the vacuumchamber so as to align the first ion source with the ion inlet orificeand wherein in a second mode of operation the assembly may be detachedthereby enabling a second different ion source to be located adjacentthe ion inlet orifice.

Conventionally, attempting to change a sub-atmospheric pressure ionsource to a different ion source is a relatively a difficult process. Incontrast, according to various embodiments a sub-atmospheric pressureion source may be easily swapped for a different ion source.

According to various embodiments the apparatus comprises an assemblyhousing a first sub-atmospheric pressure ion source. In a first mode ofoperation the assembly housing the sub-atmospheric pressure ion sourcemay be secured to a vacuum chamber of a mass spectrometer so as to alignthe first sub-atmospheric pressure ion source with the ion inletorifice. Then when it is desired to operate a different ion source, in asecond mode of operation the assembly may be detached thereby enabling asecond different ion source to be located adjacent the ion inletorifice. As a result, a non-skilled user may operate a sub-atmosphericpressure ion source located within a housing of an assembly and thensimply detach the assembly in order to use a different ion source. Forexample, the sub-atmospheric pressure ion source may be swapped for asecond atmospheric pressure or ambient ion source.

According to various embodiments the assembly or door assembly whichhoused or houses the first sub-atmospheric pressure ion source in afirst mode of operation may be re-used in order to provide a support orplatform for a second different ion source. For example, the assembly ordoor assembly may be arranged to be secured or securable to a surface ofthe instrument in order to provide a support or platform for the secondion source. According to various embodiments the assembly or doorassembly may be removably securable to the front face of a vacuumchamber of a mass spectrometer enabling an atmospheric pressure ionsource to be positioned close to an ion inlet orifice provided in a faceof the vacuum chamber.

In the first mode of operation the assembly or door assembly may make avacuum tight seal against a front face of the vacuum chamber or a vacuumchamber. However, it will be understood that in the second mode ofoperation the assembly or door assembly may be used simply as a supportor platform for the second ion source. Accordingly, in the second modeof operation the assembly or door assembly may not make a tight sealagainst the front face of the vacuum chamber or a vacuum chamber.

Conventionally, changeover from a sub-atmospheric pressure ion source toanother ion source requires the complete venting of the instrument.According to various embodiments the combination of an isolation valveand an easily removable initial ion guide enables the initial stage of amass spectrometer to be isolated thereby allowing the assembly or doorassembly housing a sub-atmospheric pressure ion guide to be pressurisedand then opened or detached. The initial ion guide may be housed in ahousing having bearings and/or a rail configuration which allows thefirst ion guide assembly to be removed and replaced with a different ionguide assembly which may be optimised for the second or alternative ionsource. In particular, the ion source can be changed and the initial ionguide assembly can also be changed or optimised without needing to ventthe entire instrument.

The assembly may comprise a door assembly.

The apparatus may comprise an ion source housing which forms a seal withthe front face of a vacuum chamber or a front face of the massspectrometer. The apparatus may further comprise a sub-atmosphericpressure ion source provided or located within the ion source housing.The ion source housing may comprise a removable door assembly.

According to various embodiments a sub-atmospheric pressure ion source,such as a Matrix Assisted Laser Desorption Ionisation (“MALDI”) ionsource, may be provided in the assembly or door assembly which may besecured to the vacuum chamber. The assembly or door assembly can beeasily detached from the vacuum chamber enabling a different type of ionsource to be used.

The assembly may comprise a translation stage.

According to various embodiments the assembly may comprise an x-ytranslation stage for translating a sample plate such as a MALDI sampleplate in one or more orthogonal directions. In particular, a laser beamor laser pulses may be arranged to emerge from the apparatus via the ioninlet orifice provided, for example, in a front face of the vacuumchamber. A sample region or a particular sample to be ionised by thelaser beam or laser pulses may be translated into position using thetranslation stage. The sample may be translated by the translation stageand different regions or portions of the sample or different samples maybe ionised by the laser beam or laser pulses. According to variousembodiments the laser beam or laser pulses may be provided in a fixedlocation or position and a sample may be translated across the laserbeam or laser pulses.

In the first mode of operation the translation stage may be translatedin a first direction perpendicular to a direction of ion transmissionthrough the ion inlet orifice and/or in a second direction which is alsoperpendicular to a direction of ion transmission through the ion inletorifice, wherein the first direction is perpendicular to the seconddirection.

According to various embodiments the assembly and translation stage mayin the first mode of operation be arranged so as to translate e.g. asample plate in an x-direction and/or a y-direction wherein thex-direction and/or the y-direction are also orthogonal to an ion-opticalaxis or z-direction which may pass through the ion inlet orifice.

The first sub-atmospheric pressure ion source may comprise a MatrixAssisted Laser Desorption Ionisation (“MALDI”) ion source.

The source or ion source may comprise a MALDI ion source although itshould be understood that the present invention is not limited to theuse of a MALDI ion source as the first sub-atmospheric pressure ionsource. If a MALDI ion source is provided then the sample chamberhousing the sample and the MALDI ion source may be enclosed and operatedunder vacuum. According to various embodiments a MALDI ion source may beprovided within an enclosure or housing which may form part of theassembly or door assembly which may engage with or secure to the frontend of the mass spectrometer (or other analytical instrument) or thefront end of a vacuum chamber or the first vacuum chamber. A small pumpmay be included to rough pump the sample chamber or housing prior toopening an isolation valve and exposing the source or ion source to theinstrument vacuum.

MALDI acquisitions generate a plume of material when a laser fires at atarget. Some of the plume of material is ionised and is onwardlytransmitted into the analyser whilst neutral species spread within thefirst vacuum chamber and are deposited on the localised surfaces. Overtime, and use, this deposit on the surface of the electrodes can affectthe electric fields generated by the electrodes and be detrimental tothe sensitivity of the instrument. As a result the first ion guideassembly requires cleaning periodically.

Conventional MALDI ion sources coupled to a mass spectrometer requirethat the instrument is fully vented in order to remove a first ionguide. In contrast, an instrument according to various embodiments doesnot need to be fully vented prior to removing a first ion guide.

In the second mode of operation the assembly may be attached to thevacuum chamber or another part of the apparatus. According to variousembodiments the assembly or door assembly which was used in a first modeof operation may be re-used to provide a support or platform for asecond different ion source. However, whereas in the first mode ofoperation the assembly or door assembly may have made a vacuum tightseal against a front face of the vacuum chamber or a vacuum chamber, inthe second mode of operation the assembly or door assembly may be usedsimply as a support or platform for the second ion source i.e. in thesecond mode of operation the assembly or door assembly may not make atight seal against the front face of the vacuum chamber or a vacuumchamber.

In the second mode of operation the assembly may include a translationstage, wherein the translation stage may be translated in a firstdirection which is parallel to a direction of ion transmission throughthe ion inlet orifice and/or in a second direction which isperpendicular to a direction of ion transmission through the ion inletorifice.

According to various embodiments the assembly and translation stage mayin the second mode of operation be arranged so as to translate e.g. asample plate in an x-direction (or a y-direction) and/or also in az-direction which may pass through the ion inlet orifice and which maybe parallel to an ion-optical axis.

The second ion source may comprise at atmospheric pressure ion source.Accordingly, various embodiments are contemplated wherein a firstsub-atmospheric pressure ion source may be exchanged for a secondatmospheric pressure ion source.

For example, the second ion source may comprise a DesorptionElectrospray Ionisation (“DESI”) ion source, a Low Temperature Plasma(“LTP”) ion source, a Direct Analysis in Real Time (“DART”) ion sourceor an Inductively Coupled Plasma (“ICP”) ion source.

According to another aspect there is provided a method comprising:

securing an assembly housing a first sub-atmospheric pressure ion sourceto a vacuum chamber having an ion inlet orifice so as to align the firstion source with the ion inlet orifice; and then

detaching the assembly and locating a second different ion sourceadjacent the ion inlet orifice.

The assembly may comprise a translation stage and the method may furthercomprise translating the translation stage in a first directionperpendicular to a direction of ion transmission through the ion inletorifice and/or in a second direction perpendicular to a direction of iontransmission through the ion inlet orifice, wherein the first directionis perpendicular to the second direction.

The method may further comprise attaching the assembly to the vacuumchamber.

The assembly may include a translation stage and the method may furthercomprise translating the translation stage in a first direction parallelto a direction of ion transmission through the ion inlet orifice and/orin a second direction perpendicular to a direction of ion transmissionthrough the ion inlet orifice.

According to an aspect there is provided an analytical instrument, massspectrometer or ion mobility spectrometer comprising apparatus asdescribed above.

According to an aspect there is provided a method of mass spectrometryor ion mobility spectrometry comprising a method as described above.

According to an aspect there is provided a method of cleaning orreplacing an ion guide comprising a method as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments will now be described, by way of example only, andwith reference to the accompanying drawings in which:

FIG. 1 shows a cross section of an isolation valve in a closed positionaccording to various embodiments, wherein the isolation valve isprovided between a first upstream ion guide assembly and a seconddownstream ion guide assembly;

FIG. 2A shows a vacuum isolation valve according to various embodimentsrotated to be in an open position and FIG. 2B shows the vacuum isolationvalve rotated to be in a closed position;

FIG. 3 shows a first ion guide assembly fitted with a guide rail forfacilitating axial alignment of a first ion guide and ensuringcontrolled extraction and insertion of the first ion guide out of andinto a first vacuum chamber and wherein contact plates provide a meansof electrical connection;

FIG. 4 shows a second assembly or housing which is arranged to receivethe first ion guide assembly, wherein the second assembly or housingcomprises two guide bearings for receiving corresponding guide rails ofthe first ion guide assembly and wherein the second assembly or housingis mounted in a first vacuum chamber and has electrical spring contactsfor making electrical contact with the first ion guide assembly;

FIG. 5A shows a press release spring latch used to locate the first ionguide in a home position and FIG. 5B shows the press release having beenoperated to enable the first ion guide assembly to be withdrawn from thefirst vacuum chamber;

FIG. 6 shows an ion guide assembly located in position and which may beremoved by releasing a clip and sliding the ion guide assembly out alongguide rails and shows a surface interface between a first vacuum chamberand the front face of a first ion guide assembly;

FIG. 7 shows a door assembly which according to various embodiments maycontain an x-y stage for a MALDI ion source and wherein the doorassembly may be configured to be removable or to be detached so as toenable one or more alternative ion sources to be fitted to the front endof the instrument; and

FIG. 8 shows an embodiment wherein a x-y stage is provided so as toallow horizontal motion for atmospheric DESI sample acquisition.

DETAILED DESCRIPTION

Various embodiments will now be described in more detail.

According to various embodiments a number of component assemblies areprovided which enable a first ion optic assembly provided at the frontend or initial stage of an analytical instrument such as a massspectrometer or ion mobility spectrometer to be removed, cleaned andthen replaced and/or reinserted in a simple manner which, for example,can be performed by a non-skilled user and which does not require theservices of a skilled engineer.

According to various embodiments a door assembly is also disclosed whichenables one ion source to be swapped for another ion source in a simplemanner without requiring a user to be skilled.

The mass spectrometer may include an ion source such as, for example, aMatrix Assisted Laser Desorption Ionisation (“MALDI”) ion sourcecomprising an enclosed sample chamber which in use is operated under avacuum or at sub-atmospheric pressure.

According to various embodiments an assembly or door assembly isdisclosed which enables a sub-atmospheric pressure ion source to beswapped for another ion source (e.g. an atmospheric pressure ion source)in a simple manner without requiring the services of a skilled engineer.

The mass spectrometer may include an ion source such as, for example, aMatrix Assisted Laser Desorption Ionisation (“MALDI”) ion source withinan enclosed sample chamber which in use may be operated under a vacuumor at sub-atmospheric pressure.

Ions generated by the ion source may be onwardly transmitted to a firstion guide which optionally may form part of a first ion optic assembly.As will be understood by those skilled in the art, the first ion guidemay become contaminated over time with deposits due to ions and/orneutral particles impacting upon the electrodes or rods forming thefirst ion guide assembly. As a result, the performance of the first ionguide may start to deteriorate and this will have a negative impact uponthe overall performance of the analytical instrument, mass spectrometeror ion mobility spectrometer.

Accordingly, in between analysis of samples it may be necessary ordesirable periodically to remove the first ion guide and any associatedfirst ion optic assembly for cleaning purposes. However, it will beappreciated that conventionally the process of removing a first ionguide for cleaning purposes will result in the high vacuum (lowpressure) in the downstream vacuum chambers being lost. This can resultin the mass spectrometer being offline or otherwise beingnon-operational for a relatively long period of time since the massspectrometer will first need to be fully vented so that the first ionguide can then be removed and then once the first ion guide has beenreinserted the high vacuum (low pressure) in the downstream analysersections of the mass spectrometer will need to be restored.

In contrast to conventional arrangements according to variousembodiments the first ion optic assembly can be removed (for example,easily removed) without needing to fully vent the analyser. As a result,the sections of the mass spectrometer downstream of the first ion guidecan be maintained at a relatively high vacuum (low pressure) whilst theion guide is serviced or replaced.

According to various embodiments an isolation valve is provided whichenables the analytical instrument, mass spectrometer or ion mobilityspectrometer downstream of the first ion optic assembly to be maintainedat a relatively high vacuum (low pressure) when the first ion guide andassociated first ion optic assembly are removed e.g. for cleaning orreplacement purposes.

FIG. 1 shows a spherical or cylindrical contoured isolation valve 1which may be provided according to various embodiments. The purpose ofthe isolation valve 1 is to isolate a downstream section of a chamber orvacuum chamber when a first upstream ion guide 2 is desired to beremoved from the chamber or vacuum chamber for cleaning purposes. Afirst upstream ion guide assembly 2 is shown in FIG. 1 . The firstupstream ion guide 2 may, for example, comprise a multipole rod setarrangement comprising e.g. a quadrupole, hexapole or octopole ionguide. From time to time it may be desired to remove the first ion guideassembly 2 from the analytical instrument, mass spectrometer or ionmobility spectrometer for cleaning purposes or optionally to replace thefirst ion guide assembly 2 if necessary (for example if the first ionguide 2 has become worn due to repeated cleaning).

As shown in FIG. 1 , the exit side or downstream end of the electrodeswhich form the first ion guide assembly 2 may have a bevelled, curved ornon-planar profile or may otherwise have a contoured profile whichallows the first ion guide assembly 2 to extend within a swept volume ofthe isolation valve 1. The isolation valve 1 may be rotated from aclosed position to an open position and the isolation valve 1 may bearranged so that when the isolation valve 1 is in a closed position thenthe isolation valve 1 has a cross-sectional profile which presents aconcave portion adjacent the downstream end of the first ion guide 2 andwhich presents a convex portion adjacent an upstream end of a seconddownstream ion guide 3.

The isolation valve 1 as shown in FIG. 1 is shown in a closed position.The isolation valve 1 may, for example, be rotatable or according toother embodiments the isolation valve 1 may be otherwise actuatedbetween an open and closed position. In a mode of operation theisolation valve 1 may be rotated into an open position by rotating theisolation valve by e.g. 90° from the closed position as shown in FIG. 1to an open position wherein the isolation valve is moved so as no longerto block an ion path between the upstream first ion guide assembly 2 anda downstream second ion guide 3.

The isolation valve 1 may have a spherical or curved contour whichallows the isolation valve 1 to be positioned within or extend withinthe inner diameter of one or more first or initial electrode(s) of asecond ion guide 3 which may be provided downstream from the first ionguide assembly 2 and the isolation valve 1. The second ion guide 3 may,for example, comprise a stacked ring ion guide 3 as shown in FIG. 1 .However, other embodiments are contemplated wherein the second ion guide3 may comprise a multipole rod set arrangement comprising a plurality ofrod electrodes. For example, the second ion guide 3 may comprise aquadrupole, hexapole or octopole arrangement. According to otherembodiments the second ion guide 3 may comprise another a stacked plateor sandwich arrangement of planar electrodes arranged generally parallelto a direction of ion travel through the second ion guide 3.

The shape and orientation of the isolation valve 1 enables the isolationvalve 1 to be inserted or otherwise positioned between the exit of afirst ion guide assembly 2 and the entrance of a second ion guideassembly 3 whilst minimising the distance between the two ion guideassemblies 2,3. As a result, when the isolation valve 1 is in a normalopen position ion transmission from the first upstream ion guide 2 tothe second downstream ion guide 3 is optimised or unaffected because ofthe close proximity of the two ion guides 2,3. In particular, since thetwo ion guides 2,3 can be located close to each other than the ionacceptance angle of the second downstream ion guide 3 may be suchsubstantially that all ions emerging from the exit of the first ionguide 2 are received at an angle falling within the ion acceptance angleof the second ion guide 3.

The isolation valve 1 may comprise a spherical or cylindrical sectionand the isolation valve 1 may be rotated by 90° between an open position(as shown in FIG. 2A) and a closed position (as shown in FIG. 2B). Theisolation valve 1 may be rotated, closed or opened either manually orautomatically. Embodiments are also contemplated wherein the isolationvalve may be positioned in an intermediate position between fully openand fully closed. For example, the isolation valve 1 may be positionedso as to be partially or slightly open/closed allowing the pressure ofthe vacuum chamber downstream of the isolation valve 1 to be carefullycontrolled. Altering the status of the isolation valve 1 allows a firstor front introduction stage of a vacuum chamber to be isolated from adownstream section of the vacuum chamber and hence from the main vacuumchamber(s) housing the mass analyser of the mass spectrometer.

Embodiments are contemplated wherein the mass analyser housed in adownstream analyser chamber or vacuum chamber may comprise a quadrupolemass analyser, a 2D or linear quadrupole mass analyser, a Paul or 3Dquadrupole mass analyser, a Penning trap mass analyser, an ion trap massanalyser, a magnetic sector mass analyser, an Ion Cyclotron Resonance(“ICR”) mass analyser, a Fourier Transform Ion Cyclotron Resonance(“FTICR”) mass analyser, an electrostatic mass analyser arranged togenerate an electrostatic field having a quadro-logarithmic potentialdistribution, a Fourier Transform electrostatic mass analyser, a FourierTransform mass analyser, a Time of Flight mass analyser, an orthogonalacceleration Time of Flight mass analyser or a linear acceleration Timeof Flight mass analyser.

The isolation valve 1 may be positioned or may be arranged to insertitself or operate between the first ion guide assembly 2 and a secondion guide assembly 3 as shown in FIG. 1 and wherein both the first andsecond ion guides 2,3 are located within the same vacuum chamber.Accordingly, the isolation valve 1 may not form a differential pumpingaperture i.e. in normal operation both the first and second ion guides2,3 may be intended to be operated at substantially the same pressure.Closing the isolation valve 1 so as to prevent fluid communicationbetween a region upstream of the isolation valve 1 and a regiondownstream of the isolation valve 1 allows the first stage of the vacuumchamber upstream of the isolation valve 1 to be vented without affectingthe vacuum in the main analyser housing and downstream vacuumchamber(s).

As shown in FIG. 1 , the ends of the electrodes of the first ion guideassembly 2 may be bevelled, curved or otherwise shaped to betteraccommodate the contour of a spherical section isolation valve 1. Inparticular, a compact arrangement can be formed which allows closepositioning of the first and second ion guides 2,3.

The first ion guide 2 can be easily removed allowing the first ion guide2 to be cleaned or replaced. In particular, the first ion guide 2 can beremoved by a non-skilled user in a safe manner without risk ofelectrocution and without risk of damaging sensitive ion-opticalcomponents and/or electrical connections.

As shown in FIG. 3 , the first ion guide 1 may be mounted to or formpart of a first ion optic assembly. According to various embodiments thefirst ion optic assembly may comprise a multipole rod set arrangementmounted at an upstream end within a circular housing or collar. Thecircular housing or collar may, as shown in FIG. 3 , further compriseone or more contact plates 6 which are arranged to connect tocorresponding electrical contacts provided in a second assembly orhousing which is arranged to engage with and interlock with the firstassembly. The first ion optic assembly may be removeable and the secondassembly or housing may be fixed.

According to various embodiments the first ion optic assembly or firstassembly which may include electrodes forming the first ion guide may bearranged to be removable whilst the second assembly may be arranged toremain in position and not to be removable, at least by a non-skilleduser.

The first assembly may include one or more plates or other planarsurfaces which may be arranged to slide into a guide provided on thesecond assembly. The first assembly may, for example, comprise one ormore bottom plates which may have guide rails 5 along the outer or sideedge of the plate(s). The guide rails 5 may be arranged to be receivedwithin and slide within one or more guide bearings 4 which may beattached to or otherwise form part of the second assembly or housing.

Embodiments are also contemplated wherein the first (removable) assemblymay comprise one or more guide bearings and the second (fixed) assemblymay comprise one or more guide mechanisms or guide rails.

Other embodiments are contemplated wherein the first assembly maycomprise one or more guide bearings and/or one or more guide mechanismsor guide rails and the second assembly may comprise one or more guidebearings and/or one or more guide mechanisms or guide rails.

Further embodiments are also contemplated wherein the second assemblymay also be removable from the vacuum chamber.

FIG. 3 shows an illustrative embodiment comprising two guide bearings 4in combination with two guide rails 5 which allows the first ion opticassembly to be drawn out and removed in a direction parallel to the ionoptic axis without the risk of accidental contact with any criticallypositioned components inside the first stage of the vacuum housing.

The axial direction of motion when inserting or removing the first ionoptic assembly 2 combined with the contoured end profiles of the firstion guide electrodes 2 and the shape or profile of the isolation valve 1allows the isolation valve 1 to swing, rotate or otherwise move from anopen or fully open position to a closed or fully closed position whilstminimising the distance between the exit of the first ion guide assembly2 and the entry or entrance region of the second ion guide assembly 3.

Removal or insertion of the ion guide 2 in a lateral direction relativeto the ion optical axis (i.e. orthogonal to the longitudinal axis of thefirst ion guide 2 and the ion optical axis) would require that theelectrodes forming the first ion guide 2 are retracted out of the volumeenclosed by the isolation valve.

Electrical connections to the first ion guide 2 may be made inside orwithin a vacuum chamber or a first vacuum chamber of a mass spectrometeror ion mobility spectrometer by means of one or more contact plates 6.The one or more contact plates 6 may form part of the first ion opticassembly 2. The one or more contact plates 6 provided as part of thefirst ion optic assembly 2 may be arranged so as to engage and providean electrical contact with one or more contacts 7 which may form part ofthe second assembly or housing.

As shown in FIG. 4 , the one or more contacts 7 which may form part ofthe second assembly or housing may comprise electrical spring contacts7. According to various embodiments the spring electrical contacts 7 maycomprise one or more pins or projections which may be notched so as toengage with a contact plate 6 provided as part of the first assembly.One or more of the contact plates 6 provided as part of the firstassembly may also have a projection, notch or other engagement mechanismfor engaging with a corresponding contact 7 provided in the secondassembly or housing. One or more of the spring contacts 7 may, forexample, be axially spring loaded so that they may be retractable ashort distance axially into the housing of the second assembly.

Embodiments are also contemplated wherein one or more contact plates 6are provided as part of the second assembly or housing and one or morecontacts or spring contacts 7 are provided as part of the firstassembly.

Yet further embodiments are contemplated wherein the first assembly maycomprise a mixture of contact plates 6 and contact or spring contacts 7and/or wherein the second assembly or housing may comprise a mixture ofcontact plates 6 and contact or spring contacts 7.

The contact plates 6 and corresponding spring contacts 7 enable thefirst ion optic assembly 2 to be removed easily and replaced without therequirement to disconnect or connect a complex series of wires or plugs.In particular, the first ion guide assembly can be electricallydisconnected and removed by a non-skilled user without risk ofelectrocution and without risk of damaging sensitive electrical powersupplies or other components located within the vacuum chamber.

The first ion guide assembly may comprise a housing having an upstreamor front face which engages with a front end, panel, flange or sectionof the mass spectrometer of first vacuum chamber. The first ion guideassembly may, for example, be arranged to be positioned in use so thatthe front face of the first ion guide assembly is essentially flush withthe front end, panel, flange or section of the first vacuum chamber ormass spectrometer. The guide rails or other engagement mechanismprovided as part of the first assembly may ensure that the first ionguide 2 can only be inserted into the first vacuum chamber of the massspectrometer in a single desired position or orientation. For example,the guide mechanism may be provided at bottom or top portions of thefirst assembly in a horizontal plane. Alternatively, the guide mechanismmay be provided in a vertical plane on one or both side portions of thefirst assembly.

The arrangement of the guide assembly may ensure that the first assemblyincluding the first ion guide 2 is only capable of being inserted intothe vacuum chamber in a correct orientation. In contrast, with a knownarrangement it may be possible inadvertently to remount the first ionguide in a different orientation to that previously with the result thatthe mass spectrometer may need to be adjusted or recalibrated in orderto ensure optimal performance.

According to various embodiments the first ion guide assembly can onlybe inserted back into the first vacuum chamber or a vacuum chamber ofthe mass spectrometer in exactly the same orientation as it waspreviously. Accordingly, no adjustment or recalibration of the massspectrometer is required once the first ion guide assembly isreinserted.

The first ion guide assembly may be locked, located or otherwise securedin a home position by, for example, a press release mechanism. Accordingto various embodiments the press release mechanism may comprise a springlatch mechanism 8 as shown in FIG. 5 . The press release mechanism orspring latch mechanism 8 allows the first assembly including the firstion guide to released or otherwise freed from being secured within thefirst vacuum chamber or a vacuum chamber of the mass spectrometer. Inparticular, the ion guide can be removed without requiring anyextraction tools and without requiring the services of a specialistengineer. According to various embodiments depressing the latch 8 freesthe assembly allowing it to be removed from the vacuum chamber.

It is contemplated, for example, that the first ion guide assembly andthe process of removing the first ion guide assembly may be performed byunskilled personnel. For example, the mass spectrometer or otheranalytical instrument might be operated by a nurse in a surgicalenvironment to analyse biological samples in a clinical setting. It isalso contemplated that the first ion guide assembly may comprise aconsumable part which when dirty may simply be replaced with a new ionguide assembly. In a military setting, for example, the massspectrometer may be operated in a field hospital and it may be desiredto prolong the useful service life of the mass spectrometer by replacingthe first ion guide assembly with a new ion guide assembly. The new ionguide assembly may comprise a cheaper, simpler or less robust componentthan the ion guide assembly which it replaces, but the purpose of thereplacement ion guide assembly may be to extend the service life of themass spectrometer especially during a period of high demand or in anemergency situation.

As shown in FIGS. 5A and 5B, the front face of the mass spectrometer orfirst vacuum chamber may include one or more projections which engage orinsert within one or more depressions, apertures or openings provided ina front face, flange or plate of the first ion guide assembly.Alternatively, the front face, flange or plate of the first ion guideassembly may include one or more projections which engage or insertwithin one or more depressions, apertures or openings provided in thefront face of the mass spectrometer or first vacuum chamber.

Other embodiments are contemplated wherein the first ion guide assemblymay use a different form of catch or latch mechanism in order to securethe first ion guide assembly in position against or within a front faceof the main body of the mass spectrometer housing or to the first vacuumchamber.

One or more apertures and/or ion extraction electrodes may be providedin the front face, flange or plate of the first ion guide assemblythrough which ions from the ion source are transmitted so that the ionsare received by the electrodes forming the first ion guide assembly.

One or more plates or ion extraction electrodes (which may be removable)may be provided in the front face, flange or plate of the first ionguide assembly, wherein the one or more plates have one or moreapertures through which ions are arranged to pass in use. The one ormore plates or ion extraction electrodes may be electrically conductiveand may be arranged to act as an electrode to guide, attract oraccelerate ions through the one or more apertures and into the first ionguide.

According to various embodiments the one or more apertures may be sizedlarger than a differential pumping aperture. According to otherembodiments the one or more apertures may be sized so as to form adifferential pumping aperture wherein in use the pressure upstream ofthe aperture is greater than the pressure downstream of the aperture.For example, the pressure upstream of the one or more apertures may bearranged to be at atmospheric or ambient pressure whereas the pressuredownstream of the one or more apertures may be arranged to be atsub-atmospheric or sub-ambient pressure. According to an embodiment anion source comprising a capillary may be located adjacent the apertureprovided in the front face, flange or plate of the first ion guideassembly.

Once the isolation valve 1 is closed, the pressure inside the firstvacuum chamber or the vacuum chamber containing or housing the first ionguide 2 can be raised to atmospheric pressure or ambient pressure by theopening of a vent valve which may fitted to a vent/pump port in thefirst vacuum chamber or in a vacuum chamber.

A number of different embodiments are contemplated in terms of how anion source may be provided adjacent the front end of the massspectrometer and optionally in relatively close proximity to one or moreion entrance apertures and/or ion extraction electrodes provided in thefront face, flange or plate of the first ion guide assembly.

For example, according to various embodiments a MALDI ion source may beprovided. The MALDI ion source may be provided within a housing whichmay form a door assembly with the front end of the mass spectrometer (orother analytical instrument) or a vacuum chamber or the first vacuumchamber.

Once the first ion guide is located in position within the vacuumchamber, the sample analysis chamber door (if present) may then beclosed. The first vacuum chamber may then be pumped using a roughingpump via a pumping port included in the first vacuum housing or ahousing of a vacuum chamber.

After the pressure in the first vacuum chamber has fallen to a levelcomparable to the pressure in the ion source, the isolation valve 1 canthen be opened, and operation of the instrument can be resumed.

However, it should be understood that many different forms of ion sourcemay be interfaced with the front face of the mass spectrometer or firstvacuum chamber and the associated first ion guide assembly positioned orlocated therewithin.

As well as allowing a rapid means of removal or replacement of an ionguide or ion guide assembly, for cleaning or other purposes, theconfiguration according to various embodiments also allows alternativeconfigurations of ion guides, ion guide and ion-optic assemblies andatmospheric sampling orifices to be introduced. For example, accordingto an embodiment an ion guide assembly may be replaced with a collisionsurface assembly.

According to an embodiment the second assembly which is provided withinthe vacuum chamber may be arranged to receive different configurationsof first ion guide or ion-optic assembly. For example, it iscontemplated that a first ion guide assembly comprising a hexapole rodset might be replaced by an ion guide assembly comprising a quadrupoleor octopole rod set arrangement.

According to other embodiments a first ion guide assembly comprisingring electrodes, apertured electrodes, rod electrodes or anotherelectrode arrangement might be replaced by a similar arrangement butwherein the internal inscribed radius or ion guiding volume is smaller,larger or has a different profile. Alternatively, quite different ionguide assemblies might be introduced. For example, a multipole rod setion guide arrangement might be replaced by a different geometry of ionguide such as an ion tunnel or ion funnel ion guide arrangement. Yetfurther embodiments are contemplated wherein one ion guide arrangementhaving a certain axial spacing of electrodes might be replaced byanother ion guide having a different axial spacing of electrodes. It isalso contemplated that one ion guide arrangement having a first form ofelectrical connection might be replaced by another ion guide arrangementhaving a second different form of electrical connection. For example,according to an embodiment an ion tunnel arrangement wherein adjacentelectrodes are maintained at opposite phases of an AC or RF voltagemight be replaced with a different ion tunnel arrangement whereinelectrodes are arranged in pairs so that two axially adjacent electrodesare maintained at a first phase of an AC or RF voltage and the next pairof axially adjacent electrodes are maintained at a second differentphase of the or an AC or RF voltage.

With reference to FIG. 6 , the interface 9 between the first vacuumchamber and the front face, flange or plate of the first ion guide maycomprise an O-ring sealing arrangement. The first ion guide assembly maycomprise an extraction electrode 10 having an aperture through whichions are transmitted in use. The aperture of the extraction electrode 10presenting to the outside of the first vacuum chamber can be reduced orthe extraction electrode 10 may be fitted with a sampling capillary suchthat the configuration forms a differential pumping aperture between thefirst vacuum chamber and the surrounding atmosphere.

Embodiments are contemplated wherein the initial electrode of the firstion optic assembly 2 can be modified from a MALDI extraction electrode,designed to operate under vacuum, having a relatively large diameteraperture, to an atmospheric sampling device with a relatively smallaperture, which can act as a differential pumping aperture.

FIG. 7 illustrates that an ion source may be provided in or locatedwithin a housing 11. The housing 11 may be maintained at sub-atmosphericpressure and the ion source may comprise a sub-atmospheric pressure ionsource. For example, according to various embodiments a MALDI ion sourcemay be provided within the housing 11. The MALDI ion source may comprisea sub-atmospheric pressure ion source. Although a MALDI ion source isshown in FIG. 7 , it will be understood that other sub-atmosphericpressure ion sources may be provided instead. Furthermore, otherembodiments are contemplated wherein an atmospheric pressure or ambiention source may be provided within the housing 11.

The housing 11 may be arranged to pivot, rotate, swing or otherwiselatch into engagement with the front face of the instrument, massspectrometer or a vacuum chamber. The housing 11 may open away from thefront face of the instrument, mass spectrometer or the vacuum chamber.According to various embodiments the ion source housing 11 may form adoor enclosure 11 so that the housing or door enclosure 11 may swing orslide into sealing engagement with the front face of the instrument,mass spectrometer or the vacuum chamber. The door enclosure 11 may havea cam arrangement such that the door enclosure 11 pushes up against thefront face of the instrument, mass spectrometer or vacuum chamber inorder to seal against it.

According to various embodiments the housing or door enclosure 11 mayhouse a MALDI sample stage. The MALDI sample stage may be operated, inuse, at sub-atmospheric pressure.

The housing or door enclosure 11 may be detachable from the front faceof the instrument, mass spectrometer or vacuum chamber. In particular,the housing or door enclosure 11 may be arranged so that it can belifted off or otherwise detached from the front face of the instrument,mass spectrometer or vacuum chamber so as to allow one or morealternative configurations of ion source to be located close to thefront face of the instrument, mass spectrometer or vacuum chamber. Inparticular, one or more alternative configurations of ion source may bepositioned or otherwise located close to the front face of theinstrument, mass spectrometer or vacuum chamber. For example, one ormore alternative ion sources may be positioned so as to abut against orclose to the front face of the instrument, mass spectrometer or vacuumchamber. The one or more alternative ion sources may be positioned so asto align the ion source with an ion inlet orifice and optionalassociated extraction electrode which may be provided in the front faceof the instrument, mass spectrometer or vacuum chamber.

It will be apparent, therefore, that in a first mode of operation thehousing or door enclosure 11 may be secured to the vacuum chamber so asto align an ion source with an ion inlet orifice. The housing or doorenclosure 11 may then be unsecured from the vacuum chamber and a seconddifferent ion source may be located or positioned close to the ion inletorifice.

According to various embodiments the housing or door enclosure 11 may bedetached from the front face of the instrument, mass spectrometer orvacuum chamber and may then be manually rotated through 90°. The housingor door enclosure 11 may then be manually re-attached to the front faceof the instrument, mass spectrometer or vacuum chamber in order toprovide a platform or mounting stage for an ion source.

It will be apparent that the whole initial stage, source or ion sourcemay open or be easily accessible thereby facilitating easy user access.

The door enclosure or mechanism 11 may be arranged to latch or otherwisesecure or lock onto the front face of the instrument, mass spectrometeror vacuum chamber so that the interior of the door enclosure forms afluid tight seal with the front face of the instrument, massspectrometer or vacuum chamber. As a result, the interior of thehousing, door housing or door enclosure or mechanism 11 including, forexample, a sample stage provided within the housing may be maintained atsub-atmospheric pressure. The housing or door enclosure 11 may have afirst connector or first device which may secure to a second connectoror second device provided on the front face of the instrument, massspectrometer or vacuum chamber. According to various embodiments thehousing or door enclosure 11 may have a projection, clip or latch whichmay secure to a corresponding projection, clip or latch provided on thefront face of the instrument, mass spectrometer or vacuum chamber.

It should, however, be understood that the provision of an ion sourcemounted within a door mechanism and maintained in use at sub-atmosphericpressure is not essential and that various embodiments are contemplatedwherein the ion source may comprise an atmospheric pressure ion source.

The housing or door enclosure 11 may enclose a translation stage such asa MALDI translation stage. The translation stage may comprise an x-ytranslation stage. The translation stage may be arranged to translate asample or multiple discrete samples in a x-direction and/or ay-direction wherein both the x-direction and the y-direction areorthogonal to a z-direction, wherein the z-direction corresponds to anion-optic axis. The ion-optic axis (and hence z-direction) may passthrough an ion inlet orifice provided in a front face of the instrument,mass spectrometer or vacuum chamber.

A laser beam or laser pulses may be arranged to pass through an ioninlet orifice provided in the front face of the instrument, massspectrometer or vacuum chamber. The laser beam or laser pulses may begenerated by a laser which is located within the instrument, massspectrometer or vacuum chamber and the laser beam or laser pulses maypass through an ion inlet orifice in a direction towards the housing ordoor enclosure 11. The laser beam or laser pulses may be arranged toimpinge upon a sample or multiple samples which may mounted upon atranslation stage located within the housing or door enclosure 11.Accordingly, the translation stage may be arranged to translate thesample or multiple samples relative to the laser beam or laser pulses inorder to ionise different portions or sections of the sample ordifferent samples. For example, the translation stage may be arranged tomove one or more samples to be analysed relative to the laser beam orlaser pulses so that a laser beam or laser pulses are effectivelyscanned across the surface of a sample or from one sample to another.

Another feature is shown in FIG. 8 wherein in a second mode of operationthe housing or door enclosure 11 may be removed or detached from thefront face of the instrument, mass spectrometer or vacuum chamber. Thehousing or door enclosure 11 may then be manually rotated through 90°.The housing or door enclosure 11 may then be manually re-attached to thefront face of the instrument, mass spectrometer or vacuum chamber.Alternatively, the housing or door enclosure 11 may simply be positionedclose to the front face of the instrument, mass spectrometer or vacuumchamber without actually being firmly attached to the front face of theinstrument, mass spectrometer or vacuum chamber.

It will be apparent that in the second mode of operation the housing ordoor enclosure 11 may no longer be utilised as a housing or doorenclosure. Instead, the housing, door assembly or door enclosure 11 mayeffectively provide a platform, support or base for a second ion sourcewhich may comprise an atmospheric pressure or an ambient ion source.

As shown in FIG. 8 , the housing or door enclosure 11 may be configuredto open such that a x-y stage or other translation stage can bepositioned horizontally providing a platform for alternative atmosphericor ambient sampling techniques. For example, an x-y stage may beprovided so as to enable spatial sampling to be employed. Variousembodiments are contemplated wherein a Desorption ElectrosprayIonisation (“DESI”) ion source, a Low Temperature Plasma (“LTP”) ionsource, a Direct Analysis in Real Time (“DART”) ion source, anInductively Coupled Plasma (“ICP”) ion source or other ion source may beprovided. In the second mode of operation wherein a second ion sourcemay be provided in a configuration as shown in FIG. 8 , then a samplemounted to a translation stage or multiple samples provided on a sampleplate may be translated in a x-direction or y-direction, wherein thex-direction and/or y-direction are orthogonal to a z-direction. Thez-direction may be parallel to an ion-optic axis which may pass throughan ion inlet orifice provided in the front face of instrument, massspectrometer or vacuum chamber.

Accordingly, in the second mode of operation the translation stage maybe translated in a direction parallel to the ion-optic axis and also ina direction perpendicular to the ion-optic axis.

In the first mode of operation when a sub-atmospheric pressure ionsource may be operated within the housing or door assembly 11 ionsgenerated by the ion source may be arranged to pass through a firstinterface. For example, the first interface may comprise an ion inletorifice together with an extraction electrode. In the second mode ofoperation when a different ion source is used such as an atmosphericpressure or ambient ion source then ions generated by the ion source maybe arranged to pass through a second different interface. The secondinterface may, for example, comprise a capillary, a nozzle-skimmerinterface or an ion inlet orifice together with an extraction electrode.The size of the ion inlet orifice may be different between the first andsecond modes of operation. Similarly, a different configuration orarrangement of extraction electrodes may be used or provided whenswitching between the first and second modes of operation.

Although the present invention has been described with reference topreferred embodiments, it will be understood by those skilled in the artthat various changes in form and detail may be made without departingfrom the scope of the invention as set forth in the accompanying claims.

1. A method comprising: sliding or translating a first ion opticassembly in cooperation with a guide mechanism, wherein the guidemechanism is part of a housing, the housing located within a vacuumchamber, said sliding or translating of the first ion optic assembly incooperation with the guide mechanism thereby enabling the first ionoptic assembly to be inserted and aligned within the vacuum chamber. 2.The method of claim 1, wherein the first ion optic assembly furthercomprises a sealing member having an ion inlet orifice therewithin,wherein the sealing member is arranged to seal against a front portionof the vacuum chamber.
 3. The method of claim 2, further comprisingusing a releasable latch to at least one of: secure the sealing memberagainst a front portion of the vacuum chamber; and secure the first ionoptic assembly within the vacuum chamber.
 4. The method of claim 2,further comprising using a releasable latch to remove or withdraw thefirst ion optic assembly from the vacuum chamber.
 5. The method of claim1, wherein the first ion optic assembly further comprises a firstelectrical connector and the housing further comprises a secondelectrical connector, and wherein the method further comprises:inserting the first ion optic assembly into the vacuum chamber therebycausing the first electrical connector to connect with the secondelectrical connector.
 6. The method of claim 1, wherein the vacuumchamber comprises a vacuum chamber ion inlet orifice, and the methodfurther comprises: securing an assembly housing a first sub-atmosphericpressure ion source to the vacuum chamber in a first mode of operationso as to align the first ion source with the vacuum chamber ion inletorifice; and detaching the assembly and locating a second different ionsource adjacent the vacuum chamber ion inlet orifice in a second mode ofoperation.
 7. The method of claim 6, further comprising: attaching theassembly to the vacuum chamber in the second mode of operation.
 8. Themethod of claim 6, wherein in the second mode of operation the assemblyincludes a translation stage, and the method further comprises at leastone of: translating the translation stage in a first direction parallelto a direction of ion transmission through the vacuum chamber ion inletorifice; and in a second direction perpendicular to a direction of iontransmission through the vacuum chamber ion inlet orifice.
 9. The methodof claim 1, wherein the first ion optic assembly comprises guide rails,and the guide mechanism of the housing comprises guide bearings, and themethod comprises sliding the guide rails of the first ion optic assemblywithin the guide bearings of the housing.
 10. Apparatus comprising: avacuum chamber; a housing located within the vacuum chamber and having aguide mechanism; and a first ion optic assembly which is slidable ortranslatable in cooperation with the guide mechanism thereby enablingthe first ion optic assembly to be inserted and aligned within thevacuum chamber.
 11. Apparatus as claimed in claim 10, wherein the firstion optic assembly further comprises a sealing member having an ioninlet orifice therewithin, wherein the sealing member is arranged toseal against a front portion of the vacuum chamber.
 12. Apparatus asclaimed in claim 11, further comprising a releasable latch for at leastone of: securing the sealing member against the front portion of thevacuum chamber; and securing the first ion optic assembly within thevacuum chamber.
 13. Apparatus as claimed in claim 10, wherein the vacuumchamber comprises a vacuum chamber ion inlet orifice, the apparatusfurther comprising an assembly housing a first sub-atmospheric pressureion source, wherein in a first mode of operation the assembly may besecured to the vacuum chamber so as to align the first ion source withthe vacuum chamber ion inlet orifice and wherein in a second mode ofoperation the assembly may be detached thereby enabling a seconddifferent ion source to be located adjacent the vacuum chamber ion inletorifice.
 14. Apparatus as claimed in claim 13 wherein in the second modeof operation the assembly may be attached to the vacuum chamber oranother part of the apparatus.
 15. Apparatus as claimed in claim 13,wherein in the second mode of operation the assembly includes atranslation stage, wherein the translation stage may be translated in atleast one of: a first direction parallel to a direction of iontransmission through the vacuum chamber ion inlet orifice; and in asecond direction perpendicular to a direction of ion transmissionthrough the vacuum chamber ion inlet orifice.
 16. The apparatus of claim10, wherein the first ion optic assembly comprises guide rails, and theguide mechanism of the housing comprises guide bearings, and the guiderails of the first ion optic assembly are slidable within the guidebearings of the housing.